Bitumen compositions as mold coatings



United States Patent 3,415,669 BITUMEN COMPOSITIONS AS MOLD COATINGSEdward G. Elste, Jr., Lutherville, Md., assignor to Chevron ResearchCompany, San Francisco, Calif., a corporation of Delaware No Drawing.Continuation-impart of application Ser. No. 478,982, Aug. 11, 1965. Thisapplication July 28, 1967, Ser. No. 656,692

5 Claims. (Cl. 117--5.1)

ABSTRACT OF THE DISCLOSURE Bitumen compositions having high totalasphaltenearomatic components to parafiinic component ratios with highautoignition temperatures for ingot mold coatings.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 478,982, filed Aug. 11,1965, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention In order to minimizescabs and other imperfections when forming steel ingots, the ingot moldis coated with various materials. The imperfections in the ingot resultbecause of the great temperature differential between the moldtemperature and the molten steel temperature. While the mold temperaturemay range between about 100 F. and 1200 F., the molten steel will be atleast about 2900 F. When pouring the molten steel, splashings willfreeze and crystallize onto an uncoated mold surface.

These solid splashings having different crystal structure from the majorportion of the ingot result in imperfections and irregularities. With aproperly coated ingot mold, the splashings fall back into the moltensteel pool.

Ingot mold coatings also provide other advantages, such as extending thelife of the mold, facilitating the release of the ingot from the mold,and reduction of ingot surface imperfections.

Because of the manner in which steel ingots are formed, the demands on amold coating are particularly stringent. The coating should besufficiently fluid, so as to permit easy application to the mold, e.g.,dipping or spraying. The composition must be relatively thermally stableat temperatures of up to 1200 F. and rapidly decompose or volatilize at1900 F. The coating should result in little, if any, flaking or ashing.In addition, the coating should adhere well to the ingot mold surfaceand provide a relatively uniform coating on the surface.

Description of the prior art US. Patent Nos. 520,076 and 1,752,725 teachthe use of tars and bituminous materials as ingot mold coatings. In anarticle in the Proceedings of Open Hearth Steel Conference, 1962, p.326, by Mr. I. F. Georgiadis, at p. 332, the use of Gilsonite anduncharacterized petroleum derivatives is taught for mold coating.

3,415,669 Patented Dec. 10, 1968 "ice SUMMARY OF THE INVENTIONDESCRIPTION OF THE PREFERRED EMBODIMENTS The ingot mold compositions ofthis invention combine about 35 to parts of an aromatic bitumen withabout 65 to 35 parts of an aromatic lubricating oil extract, moreusually from about 40 to 60 parts to about 60 to 40 parts, respectively.

In combining the bitumen and the lubricating oil extract, any methodwhich achieves homogeneity may be used. Usually, elevated temperatureswill be employed to lower the viscosity.

The final composition has a kinematic viscosity at 180 F. in the rangeof about 400 to 1,700 cst. (centistokes), more usually 400 to 1,000 cst.When practicable, the kinematic viscosity may be as low as 300 cst.

The autoignition temperature of the mold coating composition is inexcess of at least 1100 F. and will generally be in the range of 1150 F.to 1400 F. The autoignition temperature is determined as follows: Apyrometer is connected to a test plate and the temperature of the testplate raised to the desired temperature. Samples weighing 0.25 g. areplaced in a steel cup (0.5" high and 0.75" in diameter), and the cup isthen positioned on the test plate. By repeating the test upon the sampleand a standard at various temperatures and noting temperaturedifferences at which autoignitions occur, the autoignition temperatureof the test sample can be determined.

The COC (Cleveland Open Cup) flash temperature is at least 425 F. andusually in the range of about 450 to 550 F. The test procedure is ASTMD92-57.

A further desirable property is to have a post-ignition temperature ofat least 1100 F. and preferably at least about 1150 F. The post-ignitiontemperature indicates whether the mold coating may ignite after the moldhas been placed on a stool. The test is carried out as follows: The moldcoating (0.25 g.) is weighed into a steel cup /8 in diameter and 1"high, simulating the initial coating. The cup is placed for 45 secondson a hot plate having a surface temperature of about 900 F. The cup isthen put into a muffle furnace and the door closed to A". The furnacewall temperature is metered, and the temperature is recorded at whichthe mold ignites, the temperature of the mufile furnace beingsuccessively raised.

The mold coating composition will analyze to a weight ratio of thecombined weight of asphaltenes and aromatics to paraflins of at least3:1 and more usually at least 4:1. Preferably, the ratio will be atleast 5:1 and may range from 10-10021. The asphaltene content will be atleast 15% and will generally not. exceed 95 weight percent, more usuallybeing in the range of about 20 to about 90 weight percent. The aromaticswill be at least 5 weight percent and generally not exceed weightpercent, more usually being in the range of about 10 to about 55 weightpercent.

Small amounts of other materials may also be present in the mold coatingcomposition, either to enhance desirable properties of the compositionor to provide new properties for the composition. Illustrative of suchadditives are fire retardants, antioxidants, water, phosphates andantifoaming agents. Usually, these additives will not exceed 10 weightpercent of the total composition and more usually not exceed 5 weightpercent of the total composition.

BITUMEN COMPONENT As already indicated, the ingot mold composition hastwo major components: bitumen and a lubricating oil extract.

Generally, the bitumen will be derived from petroleum tar or pitchbottoms, usually obtained from thermal cracking (residua). Other sourcesof the bitumen may be used, as they provide the necessary properties.

The bitumen will have a penetration in the range of about to 15, moreusually 0 to 12 (ASTM D-61). The bitumen is further characterized byhaving a softening point in the range of about 120 to 160, more usuallyin the range of about 135 to 155 (ASTM Method D36-26).

The composition of the bitumen will have at least weight percentasphaltenes and may have as high as 95 weight percent asphaltenes, moreusually in the range of about to 90 weight percent asphaltenes. Theparaflinics will be less than 25 weight percent and preferably less thanabout 20 weight percent. The ratio of the combined Weight of asphaltenesand aromatics to paraflinics should be at least about 3:1 and preferablyin the range of about 5100:l. The aromatic or naphthenics (also calledcyclics) will generally be in the range of about 5 to 60 Weight percent,more usually in the range of about 10 to 50 weight percent.

LUBRICATING OIL EXTRACT The lubricating oil extract which is used isderived by the extraction of lubricating oil distillate with any one ofa variety of solvents, e.g., propane, furfural, cresylic acid, sulfurdioxide, etc. The raflinate thus obtained is rich in paraflinics, whilethe extract is rich in aromatics, e.g., maltenes. Generalizeddescriptions of extraction procedures may be found in US. Patent Nos.2,783,162 and 2,879,219.

The extracts composition will be as follows: at least 25 weight percent,and more usually in the range of about to 98 weight percent, aromatics;paraffinics will generally be less than 10, and more usually less than 5weight percent.

The kinematic viscosity at 140 F. of the lubricating oil extract will bein the range of about 100 to 200 cst., while the boiling range of theextract will be in the range of about 550 to 1000 F.

ILLUSTRATIVE EXAMPLES In order to demonstrate the effectiveness of thecompositions of this invention as ingot mold coatings, two samples wereprepared having the following properties and compositions:

The component determination is carried out as follows:

A 1.5 to 2.0 g. sample is weighed in a 250 ml. flask and 100 ml. ofipentane added. A condenser is fitted to the flask, which is then placedin a water bath maintained at about reflux temperature (approximately115 F.), allowing just the neck of the flask to remain above thesurface. At the end of two hours, the flask is removed from the waterbath and allowed to cool to room temperature, maintaining the condenserin place.

The above materials were tested in order to determine their utility asingot mold coating compositions. The compositions were placed on aheated plate and maintained at that temperature for about one hour andthe percent weight loss determined. The percent weight loss isconsidered an indication of the coating performance of the subject moldcoating.

In a second series of tests, the materials were heated for one hour at aprescribed temperature, then ignited at 1900 F. and the total weightloss determined to determine the volatile matter. The second stepinvolving ignition at 1900 F. and determining the percent lost isconsidered to represent the volatile matter available during the pouringof the molten metal.

Totalpercentvo1atilematter 85.1 81.4 82.9 79.9 69.3 70.9

It is evident from the above table that a major proportion of thecoating is retained on the metal surface for long periods of time atelevated temperatures, providing a protective coating for the mold andpermitting easy release and the absence of irregularities and defectsupon removal of the steel ingot from the mold.

A field test was carried out at a steel mill using ingot moldsmaintained at temperatures in the range of about 700 F. to 800 F. Thecomposition of Example I was tested and found not to flash when applied,to be readily applied by spraying and to provide a relatively smooth,even coating which was retained for long periods of time without flakingor significant ashing.

Three other ingot mold coating compositions were prepared and testedunder field conditions in steel mills. These compositions were found tobe readily applied to the ingot mold, not to flash or post-ignite, andto provide minimal amounts of imperfections and scabs on the ingotbecause of contacting of splashings with the mold. The following tableindicates the composition of the bitumen used, properties of thebitumen, properties of the lubricating oil extract, the ratio ofmaterials used, and finally, the properties and analysis of the moldcomposition.

Mats are prepared for Gooch crucibles by mixing a small amount ofasbestos fiber in water to form a suspension and then pouring thesuspension through the crucible, followed by applying suction to thecrucible until a mat of from about 0.5 to 1 mm. thickness is formed. Themat is then dried at 250 F. and weighed after cooling to roomtemperature in a desiccator.

The content of the flask is then filtered through the crucible, theflask being washed with'three 10 ml. portions of n-peutane which arealso filtered. The filtrate and washings are then transferred to aweighed 250 ml. beaker and 10 ml. of n-pentane used to wash the flaskand make the transfer quantitative. The Gooch crucibles are then driedin an oven at 250 F., while the flasks used in the original extractionare cautiously heated on a hot plate to remove the bulk of adsorbedn-pentane and then placed into a 250 F. oven for 30 minutes. The flaskand crucible are removed from the oven, cooled in a desiccator andweighed.

The above method provides a separation of asphaltenes from cyclics andparafiinics. The combined weight of material retained in the extractionflask and crucible is the weight of asphaltenes reported. This procedureis analogous to that disclosed in Kleinschmidt, L. R., .I. Research Nat.Bur. Standards, 54(3), 163 (1955).

The beaker containing the filtrate is cautiously heated until all thepentane has evaporated. The beaker is then cooled in a desiccator andweighed. Acetone is added, 35 ml. of acetone being used for each gram ofpeiitane solubles. The beaker is then placed on a hot plate, coveredwith a watch glass and allowed to slowly reflux for 10 minutes. At theend of this time, the beakers are allowed to cool at room temperatureand the n placed in a freeze chest at 10 F. for from 16 to 18 hours. Thel quid portion is then transferred to a tared beaker, and the solidresidue rinsed with two 15 ml. portions of cold acetone 10 F.), thewashings being added to the transferred supernatant liquid. The acetoneis evaporated on a hot plate and the beaker dried in a 250 F. oven toconstant we ght.

The material dissolved in the acetone is reported as cyclics (resins),while the residue is reported as parafiinics (oils). Duplicate samplescan be carried out to check the results. The above method for separatingparafilnics from cyclics is analogous to that disclosed by Traxler, R.N., and Scheyer, H. 15., Oil Gas .I., 52 158 (1953).

(In reporting component percents throughout the specification, the aboveprocedure was used.)

TABLE II III IV V Composition, Wt.:

Bitumen, percent 58 55 65 Oil extract, percent 42 45 35 Irtopertics ofmold coating composi- Viscosity at 180 F., cst 465 495 485 Autoignition,F 1, 150 1, 200 1, 250 Post-ignition- 1, 150 1, 175 1, 250 Flash,0.0.0., F 460 455 450 Fire point, F; 510 510 505 Component analysis:

Asphaltenes, percent. 24 55 54. 2 Aromatics, percent- 56 43. 4 44. 8Paraflins, percent 20 1.0 1. Coating test, 1 hr. at 800 F Visual,percent: 65 80 Weight retained, percent 32 38 Volatility, preliminaryloss at:

500 F., percent; 3. 5 2. 1 700 F., percent; 41. 4 25. 8 Ignition at1,900 F total loss 500 F. conditioned 78. 4 78. 4 700 F. conditioned-70. 2 65. 2 Properties of bitumen, component analysis:

Asphaltenes, percent 33 94. 8 90. 1 Aromatics, percent 42 5. 1 9. 8Paraffins, percent- 0. 1 0. 1 Autoignition, F. 1, 275 1, 325 1, 325Flash, 0.0.0., 9 F 500 495 Softening point, F 135 156 143 Penetration at77 12 0 Viscosity at 275212, cst 240 735 Properties of extract:

Viscosity at 140 F., cst 123 123 123 Flash, 0.0.0. F 440 440 440Autoignition, F 1, 100 1, 100 1, 100 Component anlysis:

Asphalteues, percent 0 0 0.0 0.0 Aromatics, percent 98. 0 98.0 98.0Paraflins, percent 2. 0 2. 0 2. 0

The above data effectively demonstrate that under laboratory and fieldconditions the compositions of this invention are excellent coatings foringot molds protecting against irregularities and providing improvedresults in the coating.

Moreover, the mold coating compositions of this invention may be used inthe preparation of ingots of other metals, e.g., copper. The moldcoating compositions have been demonstrated to be capable of retainingcoatings at elevated temperatures for long periods of time understringent testing and may therefore be employed with a variety of moldsand in the forming of ingots of metals other than iron.

As will be evident to those skilled in the art, various modifications onthis invention can be made or followed, in the light of the foregoingdisclosure and discussion, without departing from the spirit or scope ofthe disclosure or from the scope of the following claims.

6 I claim: 1. An improvement in the method of preparing metal ingotsusing an ingot mold at a temperature of at least 500 F. which comprisescoating the ingot mold prior to the pouring of the metal with acomposition having the following properties: a kinematic viscosity at180 F. of at least about 300 cst.; an autoignition temperature of atleast 1,100 F.; a COC flash temperature of at least 425 F.; and, aweight ratio of asphaltene and aromatic components to the parafliniccomponent of at least 3:1; and,

wherein from 35 to weight percent. of said composition is derived frombitumen of from about 0 to 15 penetration and from about to softeningpoint and having less than 25 weight percent paraffinics and greaterthan 20 weight percent asphaltenes; and

respectively, 65 to 35 weight percent of an aromatic lubricating oilextract having at least 25 weight percent aromatics and less than 10weight percent parafiinics and having a kinematic viscosity at 140 F. inthe range of about 100 to 200 est.

2. A method according to claim 1 wherein said metal is steel and whereinthe ingot is used up to a temperature of about 1,200 F.

3. A method according to claim 1 wherein the weight ratio of asphalteneand aromatic components to the paraflinic component is in the range of10 -100: 1.

4. A method according to claim 1 wherein the coating composition has anautoignition temperature in the range of about 1,150 to 1,400 E, and akinematic viscosity at F. in the range of about 400 to 1,700 est.

5. A method according to claim 4 wherein the weight ratio of theasphaltene-aromatic components to the paraflinic component is at least5: 1.

References Cited UNITED STATES PATENTS 1,752,725 4/1930 Braden 106-38252,308,245 1/ 1943 Ortynsky. 2,783,162 2/1957 Mollring 106-278 2,879,2193/1959 Benedict et a1. 106-279 XR 3,096,192 7/1963 Pitchford 106-281 aJULIUS FROME, Primary Examiner.

1.. B. HAYES, Assistant Examiner.

US. Cl. X.R.

